Intel is launching their Calpella quad-core notebook chips in the third quarter, according to DigiTimes' sources. Knowing that Apple always nicks their chips first, we probably can expect new MacBook Pros around that timeframe.
There will be three chips, successors to the CPUs in high end notebooks today: Core 2 Quad P1 (1.6GHz priced at $364 with 6MB cache,) Core 2 Quad P2 (1.73GHz at $536 with 8MB cache,) and the Core 2 Extreme XE (running at 2GHz with 8MB cache and a whopping $1,054 price tag.)
Don't hold your purchases for that, though. According to AppleInsider, there could be another refresh to the current Montevina platform, with higher speeds and price cuts "as early as this spring if it so chooses." But then again, Steve Jobs may appear naked and throwing iPhone 3.0s while dancing to Wagner's Die Valkyrie in the next WWDC as well. If he so chooses. [Apple Insider]